Process for the production of aromatic polyesters

ABSTRACT

In a continuous process for the manufacture of aromatic polyesters by polycondensation of mono- or multi-nuclear substituted or unsubstituted diphenols, with halides of aromatic dicarboxylic acids according to the two-phase interface polycondensation process, the first step is to produce continuously a fine pre-emulsion with an organic solvent and from the aqueous phase, consisting of a solution obtained from the diphenols, of an alkaline hydroxide in order to form the diphenates and possibly of a phase transfer catalyst in water or in a mixture of water and of an organic solubilizer. This pre-emulsion is fed in quantities to a dispersion unit jointly with the organo-liquid phase forming the acid chloride solution. The compounds involved in the polycondensation reaction are mixed in the dispersion unit in constant proportions in order to produce a reaction emulsion which then passes successively through one or several dispersion units and/or into static mixers, the polycondensation taking place and being completed during this period. The phases are then separated and the polyester formed is precipitated from the organic phase.

The invention relates to a process for the production of aromaticpolyesters through polycondensation of mono- or multi-nuclearsubstituted or unsubstituted diphenols with halides of aromaticdicarboxylic acid according to the two-phase interface polycondensationprocess, where from the aqueous phase, consisting of a solution of thediphenols, alkaline hydroxide for the formation of the diphenolates andpossibly a phase transfer catalyst in water or in a mixture of water andan organic solubilizer with the organo-liquid phase consisting of asolution of an acidic halide in an organic solvent, a fine reactionemulsion is produced, with the diphenolates having been converted to theorgano-liquid phase entering into polycondensation reactions with theacid halides.

Processes of the above mentioned kind have been known for a long time,for example, also from U.S. Pat. No. 3 216 970. The polycondensationprocess here is carried out as batch process, where the aqueous and theorgano-liquid phase are mixed in a reaction vessel while beingvigorously stirred and the polyester forming in the polycondensationfollowing the separation of the phases is finally precipitated from theorgano-liquid phase.

The polyesters produced according to such batch process, however,frequently have a molecular weight distribution with a relatively higholigomer component, which in many cases negatively effects, for example,the material properties of films produced from such polyesters. Inaddition, when greater batches are used in these processes thedifficulty is encountered of stirring the emulsion sufficiently, theviscosity of which increases rapidly with progressing polymer formationas well as--due to the exothermicity of the process--to maintain theemulsion at the desired low reaction temperature through high coolingexpenditures. In addition, the results of such batch processes cannotreadily be reproduced. The invention is based on the task of indicatinga process of the initially mentioned kind, which permits the productionof aromatic polyesters in large quantities in a readily reproduciblemanner, which polyesters have only a small fraction of oligomers.

The task, on which the invention is based, is solved in the processaccording to the invention, which is characterized in that for acontinuous process a fine pre-emulsion is prepared from the aqueousphase and an organic solvent, that the pre-emulsion and theorgano-liquid phase are fed into the input of a dispersing unit inquantities, that the compounds participating in the polycondensationreaction are mixed at constant proportions in the dispersing unit forthe formation of the reaction emulsion, and that the reaction emulsion,subsequently, passes sequentially through one or several dispersingunits and/or static mixers. Advantageously, the aqueous phase is thelesser component by volume in the volume of the reaction emulsion andpossibly also the pre-emulsion, so that the organo-liquid phaserespectively the organic solvent forms the continuous phase of theparticular emulsion.

The used bi-nuclear diphenols are preferrentially compounds having theformula ##STR1## in which Z is a single bond, ##STR2## a bi-functionalaliphatic hydrocarbon residue or a bi-functional hydrocarbon residuecontaining at least one aromatic or cycloaliphatic ring, as well asalkylated or halogenated derivatives of such compounds.

The process according to the invention covers also the use of mixturesof different diphenolates as well as mixtures of different acidchlorides.

According to an advantageous form of the invention, the reactionemulsion initially passes through one or several static mixers,subsequently through a dispersing unit, and, subsequently, again throughone or several static mixers.

According to a further advantageous form of the invention, the processaccording to the invention is characterized in that dispersing units areused, which each has a rotor rotating at a circumferential speed of atleast 5 m/s, preferentially, however, at least 10 m/s, provided withseveral recesses or perforations and which, in each instance, isseparated by a small mixing chamber from an associated stator, possiblylikewise provided with recesses or perforations.

Below, the process according to the invention is explained in greaterdetail in conjunction with an example.

To prepare the aqueous phase, first 92 g (2.3 Mol) NaOH and subsequently350 g (1 Mol) 9,9-bis(4-hydroxyphenyl)-fluorene are dissolved in 3 1demineralized water and 1.5 1 dioxan under the addition of heat. To thissolution 23 g (0.1 Mol) benzyltriethylammoniumchloride dissolved in 100ml demineralized water are added as phase transfer catalyst.

The organo-liquid phase consists of a solution of 101.6 g (0.5005 Mol)iso-phthaloylchloride and 101.6 g (0.5005 Mol) terephthaloylchloride in1 1 waterfree (absolute) 1,2-dichloroethane.

The drawing is a schematic representation of the arrangement used in thepresent process example.

The aqueous phase and organo-liquid phase are each cooled toapproximately 17° C. and placed in container 1 respectively 2.1,2-dichloroethane (DCE) is filled into container 3 in a quantity of6 1. In the course of the process for the production of a pre-emulsioninto the input 4 of a first dispersing unit 5 are fed: from container 3through pump 6 the DCE in the amount of 0.2 1/min and from container 1through pump 7, a heat exchanger 8, and a flow meter 9 the aqueous phasein an amount of 0.16 1/min. From the DCE and the aqueous phase in thepassage through the dispersing unit 5 a fine pre-emulsion iscontinuously produced with the DCE as continuous phase, which is removedat output 10 of dispersing unit 5.

The dispersing unit 5 is of type rotor-stator, which contains, forexample, three series-connected mixing stages, in which each mixingstage has a rotor 11 provided with, for example, slit-shapedperforations, which--in the direction of flow--follows a small mixingchamber and a stator 12 also provided with perforations. Thecircumferential speed of the rotors 11 located on a common driving shaftis approximately 17 m/s.

Concurrently with the continuous production of the pre-emulsion, fromcontainer 2 through pump 13, a heat exchanger 14 and a flow meter 15 theorgano-liquid phase consisting of the acid chlorid solution is fed in anamount of 0.04 1/min continuously and together with the pre-emulsion tothe input 18 of a second dispersing unit 19, which is structured similarto the first dispersing unit 19, in which the acid chloride solution ismixed with the DCE of the pre-emulsion and the degree of fineness of theemulsion maintained respectively further increased. In the dispersingunit 19 the polycondensation starts suddenly, with the forming polymersstaying in solution in the organo-liquid phase.

For the process to function perfectly it is important that thediphenolate dissolved in the aqueous phase and the acid chloridesupplied in the organo-liquid phase always enter into the reaction inprecisely defined constant proportions. For that purpose, the two phaseswith the aid of the two heat exchangers 8 respectively 14 are maintainedat a temperature of, for example, 17° C. and at this temperaturesupplied to the through-flow meters 9 and 15, which control--by way ofthe control circuits indicated by 16 and 17 --the delivery of pump 7respectively 13 in view of constant through-flow quantities.

The reaction emulsion removed from output 20 of the dispersing unit 19present in the form of a fine emulsion with homogeneous organo-liquidphase is transported through a first static mixer 21, subsequentlythrough a further dispersing unit 22 of the same kind as the two firstdispersing units 5 respectively 19, and, lastly, through a second staticmixer 23, whereupon the polycondensation reaction is completed. Thelength of time the reaction emulsion stays in the reaction zone, i.e.from input 18 of the dispersing unit 19 to the output of the secondstatic mixer 23 is approximately 4 minutes in the present example.

The emulsion, in which the formed polyester is dissolved in theorgano-liquid phase, is then introduced into a vessel 25 provided with astirrer 24, into which approximately 10 1 of demineralized water hadteen placed. After the solutions prepared in containers 1 and 2 has beenused up and after completion of the polycondensation process, the twophases are separated by decanting and the alkaline aqueous phasediscarded. The remaining solution of polyester in DCE is subsequentlywashed chloride-free and the polyester is precipitated followingintroduction of acetone, centrifuged, and dried at 130° C. The inherentviscosity measured at 30° C. in a solution of 0.5 g polyester in 100 mlsolvent consisting of 60 percent by weight phenol and of 40 percent byweight 1,1,2,2-tetrachloroethane was 1.62 dl/g.

With the process according to the invention polyesters can be produced,which have primarily acid end groups or phenolic end groups depending onwhether the acid chloride respectively the diphenolate are used inslight excess. Due to the hydrolysis of the acid chloride which competeswith the polycondensation, which reduces the quantity of acid chlorideavailable for the polycondensation reaction, to achieve a stoichiometricratio of the used reagents decisive for the polycondensation reaction,at which--based on experience--a maximum of the inherent viscosity isobtained, preferentially a slight acid chloride excess is used (1.001Mol acid chloride relative to 1 Mol diphenolate in the present example).

I claim:
 1. A continuous process for producing an aromatic polyester bypolycondensing at least one mono- or multinuclear substituted diphenolas first reactant with at least one aromatic dicarboxylic acid halide assecond reactant comprising:preparing an aqueous phase by mixing the saidat least one diphenol, an alkali metal hydroxide for the formation ofdiphenolates with or without a phase transfer catalyst, water or amixture of water and an organic solubilizer; preparing an organic liquidphase by mixing the said at least one aromatic dicarboxylic acid halideand an organic solvent to form a solution thereof; continuously mixingthe aqueous phase with an organic solvent to form a fine pre-emulsion;preparing a reaction emulsion by continuously supplying organic liquidphase and pre-emulsion to an input of a dispersing unit wherebyreactants in said phase and pre-emulsion are mixed in constantproportions; passing and reacting the reaction emulsion through at leastone dispersing unit.
 2. The process of claim 1 comprising passing thereaction emulsion in addition to its passing through dispersing units,through a static mixer or through several static mixers.
 3. The processof claim 2 wherein the reaction emulsion passes first through one orseveral static mixers subsequently through a dispersing unit andsubsequently again through one or several static mixers.
 4. The processof claim 1 wherein in the reaction emulsion the volume of the aqueousphase is smaller than the volume of the other phase of the reactionemulsion.
 5. The process of claim 4 comprising passing the reactionemulsion in addition to its passing through dispersing units, through astatic mixer or through several static mixers.
 6. The process of claim 4wherein in he fine pre-emulsion the volume of the aqueous phase issmaller than the volume of the organic solvent.
 7. The process of claim1 wherein the dispersing units have a rotor rotating at acircumferential speed of at least 5 meters per second which is providedwith several recesses or perforations, and which, in each instance, isseparated by a small mixing chamber from an associated stator alsoprovided with recesses or perforations.
 8. The process of claim 7wherein said dispersing units have a rotor rotating at a circumferentialspeed of at least 10 meters per second.